Iza-bren trial results announced by Bristol Myers Squibb and SystImmune on October 23, 2026, showed that the investigational breast cancer treatment reduced the risk of disease progression or death by 59% versus chemotherapy. The prespecified interim analysis of Phase 3 PANKU-Breast01 found median progression-free survival of 8.2 months with izalontamab brengitecan, compared with 4.0 months for chemotherapy.
Key Takeaways
- The Phase 3 study enrolled patients with advanced HR-positive/HER2-negative breast cancer after prior chemotherapy.
- The objective response rate was 40.5% with iza-bren, versus 20.2% with chemotherapy.
- Treatment-related adverse events led 1.6% of iza-bren patients to discontinue treatment.
Table of Contents
- Iza-bren trial extends time without disease progression
- Safety findings include blood-related adverse events
- Bristol Myers partnership advances an investigational treatment
- Conclusion
Iza-bren trial extends time without disease progression
Bristol Myers Squibb’s PANKU-Breast01 interim results announcement describes a randomized comparison in patients with unresectable locally advanced, recurrent or metastatic hormone receptor-positive, HER2-negative breast cancer. Participants had failed at least one previous line of chemotherapy.
Median progression-free survival was 4.2 months longer with iza-bren than with chemotherapy. This endpoint measures time before disease progression or death; it should not be interpreted as a demonstrated improvement in overall survival.
The objective response rate was roughly twice that of chemotherapy, providing a separate measure of antitumor activity alongside the progression-free survival result.
| Item | Details |
|---|---|
| Study groups | 190 patients received iza-bren; 193 received chemotherapy. |
| Median PFS follow-up | 15.2 months. |
| Primary endpoint assessment | Progression-free survival assessed by blinded independent central review. |
| Reported hazard ratio | 0.41, with a 95% confidence interval of 0.33–0.53. |
Safety findings include blood-related adverse events
The companies described the safety profile as manageable and said no new safety signals were identified. Grade 3 or higher treatment-related adverse events were predominantly hematologic, meaning they involved the blood or blood-forming system.
Adjudicated interstitial lung disease occurred in two iza-bren patients, or 1.1%, with cases classified as Grade 1 or 2. The low treatment-discontinuation rate does not mean the drug was free of significant adverse effects.
Bristol Myers partnership advances an investigational treatment
Iza-bren is a bispecific antibody-drug conjugate designed to target EGFR and HER3 and deliver a cancer-killing payload. The drug remains investigational; the positive interim findings are not a regulatory approval.
Sichuan Biokin Pharmaceutical, SystImmune’s parent company, sponsors PANKU-Breast01 in Mainland China. Outside China, SystImmune and Bristol Myers Squibb jointly develop iza-bren under a collaboration and exclusive license agreement.
For Bristol Myers Squibb, the findings represent a clinical development milestone rather than a reported revenue contribution. The announcement did not establish an approval timetable or quantify potential sales.
Conclusion
The Iza-bren trial showed longer progression-free survival than chemotherapy in this previously treated breast cancer population. At the time of the announcement, the next confirmed disclosure was an October 23 presentation at ESMO 2026, with simultaneous publication planned in The Lancet.
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